package com.renbang.utils.messgedigest;

import java.security.Key;  
import java.security.KeyFactory;  
import java.security.KeyPair;  
import java.security.KeyPairGenerator;  
import java.security.PrivateKey;
import java.security.PublicKey;  
import java.security.spec.PKCS8EncodedKeySpec;  
import java.security.spec.X509EncodedKeySpec;  
import java.util.HashMap;  
import java.util.Map;  

import javax.crypto.Cipher;  
import javax.crypto.KeyAgreement;  
import javax.crypto.SecretKey;  
import javax.crypto.interfaces.DHPrivateKey;  
import javax.crypto.interfaces.DHPublicKey;  
import javax.crypto.spec.DHParameterSpec;  

/** 
 * DH安全编码组件 
 *  
 * @author 梁栋 
 * @version 1.0 
 * @since 1.0 
 */  
public abstract class DHCoder extends Coder {  
    public static final String ALGORITHM = "DH";  

    /** 
     * 默认密钥字节数 
     *  
     * <pre> 
     * DH 
     * Default Keysize 1024   
     * Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive). 
     * </pre> 
     */  
    private static final int KEY_SIZE = 1024;  

    /** 
     * DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法。 
     */  
    public static final String SECRET_ALGORITHM = "DES";  
    private static final String PUBLIC_KEY = "DHPublicKey";  
    private static final String PRIVATE_KEY = "DHPrivateKey";  

    /** 
     * 初始化甲方密钥 
     *  
     * @return 
     * @throws Exception 
     */  
    public static Map<String, Object> initKey() throws Exception {  
    	//用于生成密钥对类
        KeyPairGenerator keyPairGenerator = KeyPairGenerator  
                .getInstance(ALGORITHM);  
        keyPairGenerator.initialize(KEY_SIZE);  
        //密钥对类
        KeyPair keyPair = keyPairGenerator.generateKeyPair();  

        // 甲方公钥  
        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();  

        // 甲方私钥  
        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();  

        Map<String, Object> keyMap = new HashMap<String, Object>(2);  

        keyMap.put(PUBLIC_KEY, publicKey);  
        keyMap.put(PRIVATE_KEY, privateKey);  
        return keyMap;  
    }  

    /** 
     * 初始化乙方密钥 
     *  
     * @param key 
     *            甲方公钥 
     * @return 
     * @throws Exception 
     */  
    public static Map<String, Object> initKey(String key) throws Exception {  
        // 解析甲方公钥  
        byte[] keyBytes = decryptBASE64(key);  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);  
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);  

        // 由甲方公钥构建乙方密钥  
        DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();  

        KeyPairGenerator keyPairGenerator = KeyPairGenerator  
                .getInstance(keyFactory.getAlgorithm());  
        keyPairGenerator.initialize(dhParamSpec);  

        KeyPair keyPair = keyPairGenerator.generateKeyPair();  

        // 乙方公钥  
        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();  

        // 乙方私钥  
        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();  

        Map<String, Object> keyMap = new HashMap<String, Object>(2);  

        keyMap.put(PUBLIC_KEY, publicKey);  
        keyMap.put(PRIVATE_KEY, privateKey);  

        return keyMap;  
    }  

    /** 
     * 加密<br> 
     *  
     * @param data 
     *            待加密数据 
     * @param publicKey 
     *            甲方公钥 
     * @param privateKey 
     *            乙方私钥 
     * @return 
     * @throws Exception 
     */  
    public static byte[] encrypt(byte[] data, String publicKey,  
            String privateKey) throws Exception {  

        // 生成本地密钥  
        SecretKey secretKey = getSecretKey(publicKey, privateKey);  

        // 数据加密  
        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);  

        return cipher.doFinal(data);  
    }  

    /** 
     * 解密<br> 
     *  
     * @param data 
     *            待解密数据 
     * @param publicKey 
     *            乙方公钥 
     * @param privateKey 
     *            乙方私钥 
     * @return 
     * @throws Exception 
     */  
    public static byte[] decrypt(byte[] data, String publicKey,  
            String privateKey) throws Exception {  

        // 生成本地密钥  
        SecretKey secretKey = getSecretKey(publicKey, privateKey);  
        // 数据解密  
        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, secretKey);  

        return cipher.doFinal(data);  
    }  

    /** 
     * 构建密钥 
     *  
     * @param publicKey 
     *            公钥 
     * @param privateKey 
     *            私钥 
     * @return 
     * @throws Exception 
     */  
    private static SecretKey getSecretKey(String publicKey, String privateKey)  
            throws Exception {  
        // 初始化公钥  
        byte[] pubKeyBytes = decryptBASE64(publicKey);  

        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(pubKeyBytes);  
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);  

        // 初始化私钥  
        byte[] priKeyBytes = decryptBASE64(privateKey);  

        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(priKeyBytes);  
        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);  
        //此类提供密钥协定（或密钥交换）协议的功能
        KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory  
                .getAlgorithm());  
        keyAgree.init(priKey);  
        //用给定密钥执行此密钥协定的下一个阶段，给定密钥是从此密钥协定所涉及的其他某个参与者那里接收的。
        keyAgree.doPhase(pubKey, true);  

        // 生成本地密钥  
        SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);  

        return secretKey;  
    }  

    /** 
     * 取得私钥 
     *  
     * @param keyMap 
     * @return 
     * @throws Exception 
     */  
    public static String getPrivateKey(Map<String, Object> keyMap)  
            throws Exception {  
        Key key = (Key) keyMap.get(PRIVATE_KEY);  

        return encryptBASE64(key.getEncoded());  
    }  

    /** 
     * 取得公钥 
     *  
     * @param keyMap 
     * @return 
     * @throws Exception 
     */  
    public static String getPublicKey(Map<String, Object> keyMap)  
            throws Exception {  
        Key key = (Key) keyMap.get(PUBLIC_KEY);  

        return encryptBASE64(key.getEncoded());  
    }  
}  